Volume-outcome relationship in adrenal surgery from 2009-2017 in Germany-a retrospective study

Adrenal resections are rare procedures of a heterogeneous nature. While recent European guidelines advocate a minimum annual caseload for adrenalectomies (6 per surgeon), evidence for a volume-outcome relationship for this surgery remains limited.

A retrospective analysis of all adrenal resections in Germany between 2009 and 2017 using hospital billing data was performed. Hospitals were grouped into three tertiles of approximately equal patient volume.

Descriptive, univariate, and multivariate analyses were applied to identify a possible volume-outcome relationship (complications, complication management, and mortality).

Around 17 040 primary adrenal resections were included. Benign adrenal tumors (n = 8,213, 48.2%) and adrenal metastases of extra-adrenal malignancies (n = 3582, 21.0%) were the most common diagnoses. Six hundred and thirty-two low-volume hospitals performed an equal number of resections as 23 high-volume hospitals (median surgeries/hospital/year 3 versus 31, P < .001). Complications were less frequent in high-volume hospitals (23.1% in low-volume hospitals versus 17.3% in high-volume hospitals, P < .001). The most common complication was bleeding in 2027 cases (11.9%) with a mortality of 4.6% (94 patients). Overall in-house mortality was 0.7% (n = 126). Age, malignancy, an accompanying resection, complications, and open surgery were associated with in-house mortality. In univariate analysis, surgery in high-volume hospitals was associated with lower mortality (OR: 0.47, P < .001). In a multivariate model, the tendency remained equal (OR: 0.59, P = .104). Regarding failure to rescue (death in case of complications), there was a trend toward lower mortality in high-volume hospitals.

The annual caseload of adrenal resections varies considerably among German hospitals. Our findings suggest that surgery in high-volume centers is advantageous for patient outcomes although fatal complications are rare.